Optimization of the dilution parameters to improve wear resistance of laser cladding 15-5PH steel coating on U75V pearlitic steel

Abstract

The dilution effect of the substrate during laser cladding is inherent, and controlling the dilution degree paves the way for the microstructural design of coatings with excellent mechanical properties. In this study, low-carbon 15–5 precipitation hardening (PH) stainless steel was selected as the cladding material on the surface of U75V pearlitic railway steels to improve wear performance. By altering the processing parameters, the cracking susceptibility, microstructures, and wear resistance of coatings with different dilution rates were investigated thoroughly. The results indicated that with the increase of laser beam power, the dilution effect of the eutectoid steel substrate enhanced obviously, resulting in the composition deviation of coatings. Microhardness of the coatings increased with the dilution rate but the excessive dilution effect led to severe cracking defects. The optimized cladding coating with a dilution rate of about 48 % exhibited a microhardness of 490 HV, and the wear tests showed that the wear volume decreased by about 85 % when compared to that of the U75V substrate. Microstructural characterization revealed that the increased carbon content induced by dilution, resulting in martensite hardening and carbides precipitation, was responsible for these performance improvements. This work demonstrated the potential of coating strengthening by dilution control, which expands the option for surface modification materials for railways.